Indium phosphide single-crystal body and indium phosphide single-crystal substrate

ABSTRACT

An indium phosphide single-crystal body has an oxygen concentration of less than 1×10 16  atoms·cm −3 , and includes a straight body portion having a cylindrical shape, wherein a diameter of the straight body portion is more than or equal to 100 mm and less than or equal to 150 mm or is more than 100 mm and less than or equal to 150 mm. An indium phosphide single-crystal substrate has an oxygen concentration of less than 1×10 16  atoms·cm −13 , wherein a diameter of the indium phosphide single-crystal substrate is more than or equal to 100 mm and less than or equal to 150 mm or is more than 100 mm and less than or equal to 150 mm.

TECHNICAL FIELD

The present invention relates to an indium phosphide single-crystal bodyand an indium phosphide single-crystal substrate. The presentapplication claims a priority based on International ApplicationPCT/JP2017/024460 filed on Jul. 4, 2017, the entire content of which isincorporated herein by reference.

BACKGROUND ART

A compound semiconductor substrate, such as an indium phosphidesubstrate, has been suitably used as a substrate of a semiconductordevice. It has been required to develop a compound semiconductorsubstrate on which a high-quality epitaxial layer can be grown to form asemiconductor device having high characteristics.

Japanese Patent Laying-Open No. 2002-114600 (Patent Literature 1)discloses an InP (indium phosphide) single-crystal substrate having anoxygen atom concentration falling within a range of 1×10¹⁷ atoms/cm³ to1×10¹⁸ atoms/cm³ in order to suppress occurrence of hillock (abnormalgrowth appearing on a surface of the epitaxial layer in the form of aprotrusion; the same applies to the description below) in an epitaxiallayer layered on the InP substrate.

Moreover, in order to form a semiconductor device having highcharacteristics by reducing an impurity element concentration of asubstrate and growing a high-quality epitaxial layer thereon, JapaneseNational Patent Publication No. 2016-519642 (Patent Literature 2)discloses a group III-V semiconductor substrate containing oxygen,wherein the level of the oxygen concentration can be controlled bysupplying a material having high chemical reactivity with oxygen, andthe oxygen concentration is controlled to fall within a range of1.2×10¹⁶ to 6×10¹⁷atoms cm⁻³

CITATION LIST Patent Literature

PTL 1: Japanese Patent Laying-Open No. 2002-114600

PTL 2: Japanese National Patent Publication No. 2016-519642

SUMMARY OF INVENTION

An indium phosphide single-crystal body according to the presentdisclosure has an oxygen concentration of less than 1×10¹⁶ atoms·cm⁻³,and includes a straight body portion having a cylindrical shape, whereina diameter of the straight body portion is more than or equal to 100 mmand less than or equal to 150 mm or is more than 100 mm and less than orequal to 150 mm.

An indium phosphide single-crystal substrate according to the presentdisclosure has an oxygen concentration of less than 1×10¹⁶ atoms·cm⁻³,wherein a diameter of the indium phosphide single-crystal substrate ismore than or equal to 100 mm and less than or equal to 150 mm or is morethan 100 mm and less than or equal to 150 mm.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic cross sectional view showing exemplarymanufacturing method and manufacturing apparatus for an indium phosphidesingle-crystal body in the present disclosure.

FIG. 2 is a schematic plan view showing an exemplary closure plate usedin the manufacturing method and manufacturing apparatus for the indiumphosphide single-crystal body in the present disclosure.

FIG. 3 is a schematic cross sectional view showing exemplary, typicalmanufacturing method and manufacturing apparatus for an indium phosphidesingle-crystal body.

DETAILED DESCRIPTION Problem to be Solved by the Present Disclosure

Since the InP single-crystal substrate disclosed in Japanese PatentLaying-Open No. 2002-114600 (Patent Literature 1) has a comparativelyhigh oxygen atom concentration falling within a range of 1×10¹⁷atoms/cm³ to 1×10¹⁸ atoms/cm³, a naturally oxidized film is facilitatedto be formed in a surface of the InP single-crystal substrate. Hence,when an epitaxial layer is grown on such a surface, an oxide layerhaving an insulating property is formed at an interface between thesubstrate and the epitaxial layer, thus resulting in a high resistanceof a semiconductor device to be obtained, disadvantageously. Moreover,since the oxygen atom concentration in the InP single-crystal substrateis comparatively high, free electrons are highly likely to be trapped bya composite state formed by oxygen and other impurity elements, thusresulting in a low response speed of a semiconductor device includingsuch an InP single-crystal substrate, disadvantageously.

Although the group III-V semiconductor substrate disclosed in JapaneseNational Patent Publication No. 2016-519642 (Patent Literature 2) iscontrolled to have a comparatively low oxygen concentration fallingwithin a range of 1.2×10¹⁶ to 6×10¹⁷atoms·cm⁻³, this is stillinsufficient to solve the above-described problem.

Accordingly, in order to solve the above-described problem, an object ofthe present disclosure is to provide an indium phosphide single-crystalbody and an indium phosphide single-crystal substrate, each of which hasa very low oxygen concentration.

Advantageous Effect of the Present Disclosure

According to the present disclosure, there can be provided an indiumphosphide single-crystal body and an indium phosphide single-crystalsubstrate, each of which has a very low oxygen concentration.

Description of Embodiments

First, embodiments of the present invention are listed and described.

[1] An indium phosphide single-crystal body according to one embodimentof the present invention has an oxygen concentration of less than 1×10¹⁶atoms·cm⁻³, and includes a straight body portion having a cylindricalshape, wherein a diameter of the straight body portion is more than orequal to 100 mm and less than or equal to 150 mm. In the indiumphosphide single-crystal body according to the present embodiment, theoxygen concentration is very low even though the diameter of thestraight body portion of the indium phosphide single-crystal body is solarge as to be more than or equal to 100 mm and less than or equal to150 mm.

[2] An indium phosphide single-crystal body according to one embodimentof the present invention has an oxygen concentration of less than 1×10¹⁶atoms·cm⁻³, and includes a straight body portion having a cylindricalshape, wherein a diameter of the straight body portion is more than 100mm and less than or equal to 150 mm. In the indium phosphidesingle-crystal body according to the present embodiment, the oxygenconcentration is very low even though the diameter of the straight bodyportion of the indium phosphide single-crystal body is so large as to bemore than 100 mm and less than or equal to 150 mm.

[3] An indium phosphide single-crystal substrate according to oneembodiment of the present invention has an oxygen concentration of lessthan 1×10¹⁶ atoms·cm⁻³, wherein a diameter of the indium phosphidesingle-crystal substrate is more than or equal to 100 mm and less thanor equal to 150 mm. In the indium phosphide single-crystal substrateaccording to the present embodiment, the oxygen concentration is verylow even though the diameter of the indium phosphide single-crystalsubstrate is so large as to be more than or equal to 100 mm and lessthan or equal to 150 mm.

[4] An indium phosphide single-crystal substrate according to oneembodiment of the present invention has an oxygen concentration of lessthan 1×10¹⁶ atoms-cm⁻³, wherein a diameter of the indium phosphidesingle-crystal substrate is more than 100 mm and less than or equal to150 mm. In the indium phosphide single-crystal substrate according tothe present embodiment, the oxygen concentration is very low even thoughthe diameter of the indium phosphide single-crystal substrate is solarge as to be more than 100 mm and less than or equal to 150 mm.

Details of Embodiments

<First Embodiment: Indium Phosphide Single-Crystal Body>

An InP (indium phosphide) single-crystal body of the present embodimenthas an oxygen concentration of less than 1×10¹⁶ atoms·cm⁻³, and includesa straight body portion having a cylindrical shape, wherein a diameterof the straight body portion is more than or equal to 100 mm and lessthan or equal to 150 mm or is more than 100 mm and less than or equal to150 mm. Although the diameter of the straight body portion of the InPsingle-crystal body of the present embodiment is so large as to be morethan or equal to 100 mm and less than or equal to 150 mm or as to bemore than 100 mm and less than or equal to 150 mm, the oxygenconcentration of the InP single-crystal body is less than 1×10¹⁶atoms·cm⁻³, which is very low. Accordingly, an oxide layer is suppressedfrom being formed in a surface of the InP single-crystal body and acomposite state is suppressed from being formed in the InPsingle-crystal body, whereby a semiconductor device including the InPsingle-crystal body has high characteristics. The oxygen concentrationof the InP single-crystal body is measured by SIMS (Secondary Ion MassSpectrometry). Here, since an oxygen detection limit concentration inSIMS is about 1×10¹⁶ atoms·cm³, the oxygen concentration of the InPsingle-crystal body of the present embodiment is less than the detectionlimit in SIMS, and a precise oxygen concentration thereof is measured byCPAA (Charged Particle Activation Analysis) or the like. In order toimprove the characteristics of the semiconductor device by reducing theoxygen concentration, the precise oxygen concentration of the InPsingle-crystal body of the present embodiment as obtained by theactivation analysis such as CPAA is preferably less than or equal to9.5×10¹⁵ atoms·cm'³, and is more preferably less than or equal to5.5×10¹⁵ atoms·cm⁻³. Moreover, a lower oxygen concentration is morepreferable. Although not particularly limited, the lower limit of theoxygen concentration is more than or equal to 5×10¹⁴ atoms·cm⁻³ in viewof a current manufacturing technology level.

Since the InP single-crystal body of the present embodiment is oftenmanufactured by, but not particularly limited to, a boat method such asa VB (Vertical Bridgman) method or a VGF (Vertical Gradient Freezing)method as described below, the InP single-crystal body includes astraight body portion having a cylindrical shape, and the diameter ofthe straight body portion is more than or equal to 100 mm and less thanor equal to 150 mm. Even though the diameter of the straight bodyportion of the InP single-crystal body is so large as to be more than orequal to 100 mm and less than or equal to 150 mm, the oxygenconcentration is very low. Accordingly, an oxide layer is suppressedfrom being formed in a surface of the InP single-crystal body and acomposite state is suppressed from being formed in the InPsingle-crystal body, whereby a semiconductor device including the InPsingle-crystal body has high characteristics. In order to attain the lowoxygen concentration even in the large-sized InP single-crystal body,the diameter of the straight body portion is more than or equal to 100mm, is preferably more than 100 mm, and is more preferably more than orequal to 125 mm. For the same reason, the length of the straight bodyportion is preferably more than or equal to 70 mm, and is morepreferably more than or equal to 100 mm.

Although not particularly limited, it is preferable that the InPsingle-crystal body of the present embodiment specifically has a shapeincluding: a cylindrical small-diameter portion having a small diameter;a conical portion that is connected to the small-diameter portion andthat has a gradually increasing diameter; and a cylindrical straightbody portion that is connected to the conical portion and that has adiameter larger than the diameter of the small-diameter portion. Such ashape is suitably formed by the below-described boat method such as theVB method or the VGF method.

With reference to FIG. 1, although not particularly limited, amanufacturing apparatus 20 for the InP single-crystal body of thepresent embodiment preferably includes a crucible 21, a crucible holder22, a sealing member 23, heaters 24 a, 24 b, a closure plate 25, and achamber 26 in order to efficiently manufacture the InP single-crystalbody having an oxygen concentration of less than 1×10¹⁶ atoms·cm⁻³.

Crucible 21 includes a seed crystal holding portion and a single-crystalgrowth portion connected onto the seed crystal holding portion. The seedcrystal holding portion is a hollow cylindrical portion that opens at aside connected to the single-crystal growth portion and that is providedwith a bottom wall at a side opposite thereto. At this portion, InP seedcrystal 11 can be held. The single-crystal growth portion includes: aconical portion having a conical shape and connected to the seed crystalholding portion at the small-diameter side in the axial direction; and ahollow cylindrical straight body portion connected to the large-diameterside of the conical portion in the axial direction. The single-crystalgrowth portion has a function of holding an InP source material 13therein and growing the InP single-crystal body by solidifying heatedInP source material 13 in a molten state.

Here, a material of crucible 21 is not particularly limited as long asthe material has a high mechanical strength and can withstand atemperature at which the source material is melted. For example, PBN(pyrolytic boron nitride) can be employed suitably therefor. Moreover,in order to avoid molten InP source material 13 from coming into directcontact with crucible 21, an oxide film 21 c, such as a boron oxidefilm, is preferably formed on the inner wall surface of crucible 21 as asealing member. Examples of the boron oxide film include a B₂O₃ film andthe like. For example, the B₂O₃ film can be formed on the inner wallsurface of crucible 21 by treating crucible 21, which is composed ofPBN, at a high temperature of more than or equal to 1150° C. in anatmosphere containing more than or equal to 10 volume % of oxygen.

A material of sealing member 23 is not particularly limited as long asthe material can withstand the temperature at which the source materialis melted. A boron oxide, such as B₂O₃, can be employed suitablytherefor.

The plurality of heaters 24 a, 24 b are normally placed to appropriatelycontrol the melting and solidification of InP source material 13;however, in order to reduce the oxygen concentration in the InPsingle-crystal body to be grown, a smaller number of inter-heater gapsare preferably provided. One inter-heater gap is preferably provided.That is, a smaller number of heaters are preferably provided. Twoheaters are preferably provided.

Closure plate 25 is preferably disposed between InP source material 13and sealing member 23 in order to reduce the oxygen concentration in theInP single-crystal body to be grown. A material of closure plate 25 isnot particularly limited as long as the material has a high mechanicalstrength and can withstand a temperature at which the source material ismelted. For example, PBN (pyrolytic boron nitride) can be employedsuitably therefor. A closure ratio (percentage of the area of theclosure plate with respect to the cross sectional area of the straightbody portion of crucible 21 perpendicular to the axial direction; thesame applies to the description below) of closure plate 25 is preferablymore than or equal to 85% and less than 100% and is more preferably morethan or equal to 90% and less than or equal to 98% in order to reducethe oxygen concentration in the InP single-crystal to be grown andprevent breakage of the crucible. It should be noted that with referenceto FIG. 2, closure plate 25 may be provided with an opening 25 o foradjusting the closure ratio.

With reference to FIG. 1, although not particularly limited, in order toefficiently grow the InP single-crystal body having a low oxygenconcentration, a method for manufacturing the InP single-crystal body inthe present embodiment is preferably based on the boat method, such asthe VB (Vertical Bridgman) method or the VGF (Vertical GradientFreezing) method, using the above-described manufacturing apparatus 20.Specifically, the method for manufacturing the InP single-crystal bodyin the present embodiment preferably includes an InP seed crystalloading step, an InP source material loading step, a closure plateplacing step, a sealing member placing step, and a single-crystalgrowing step.

First, manufacturing apparatus 20 is used to load InP seed crystal 11 inthe seed crystal holding portion of crucible 21 in the InP seed crystalloading step. Next, in the InP source material loading step, InP sourcematerial 13 is loaded in the single-crystal growth portion (the conicalportion and the straight body portion) of crucible 21. Here, the InPsource material is not particularly limited as long as it is InP havinghigh purity (for example, more than or equal to 99.9 mass %). An InPpolycrystal body, an InP single-crystal body, or the like is usedsuitably therefor. Next, in the closure plate placing step, closureplate 25 is placed on InP source material 13 in crucible 21. Next, inthe sealing member placing step, sealing member 23 is placed on closureplate 25 in crucible 21.

Next, in the single-crystal growing step, crucible 21 in which InP seedcrystal 11, InP source material 13, closure plate 25, and sealing member23 are disposed in this order from below to above is loaded in crystalapparatus 20. Crucible 21 is held by crucible holder 22, and heaters 24a, 24 b are disposed to surround crucible 21. Next, crucible 21 isheated by supplying electric current to heaters 24 a, 24 b. Accordingly,InP source material 13 is melted into a melt and sealing member 23 isalso melted into a liquid sealing member. Moreover, an oxide film isformed in the inner wall of crucible 21 due to oxidation of the materialof crucible 21.

On this occasion, the melt of the InP source material is stirred byconvection currents generated due to local low-temperature portionsformed by the presence of inter-heater gap 24 abo between heater 24 aand heater 24 b. The stirred InP source material is brought into contactwith oxide film 21 c of the inner wall of crucible 21 and/or sealingmember 23, whereby oxygen included in oxide film 21 c of the inner wallof crucible 21 and/or sealing member 23 is presumably incorporated intothe InP source material. Here, with reference to FIG. 3, in a typicalmanufacturing apparatus 30, three or more heaters 34 a, 34 b, 34 c, 34 dare disposed. Hence, there are two or more inter-heater gaps 34 abo, 34bco, and 34 cdo. Accordingly, many convection currents are generated byresultant local low-temperature portions, with the result that a largeamount of oxygen included in oxide film 31 c of the inner wall ofcrucible 31 and/or sealing member 33 is incorporated into the InP sourcematerial. On the other hand, with reference to FIG. 1, only two heaters24 a, 24 b are disposed in manufacturing apparatus 20 of the presentembodiment. Hence, there is only one inter-heater gap 24 abo.Accordingly, fewer convention currents are generated by resultant locallow-temperature portions, with the result that oxygen is suppressed frombeing incorporated into InP source material 13.

Further, in manufacturing apparatus 20 of the present embodiment,closure plate 25 is disposed between InP source material 13 and sealingmember 23. Accordingly, contact between InP source material 13 andsealing member 23 is suppressed, with the result that oxygen issuppressed from being incorporated in InP source material 13.

Next, a temperature gradient in which a temperature at the InP seedcrystal 11 side is relatively low and a temperature at the InP sourcematerial 13 side is relatively high in the axial direction of crucible21 is formed by moving crucible 21 to the lower side in the axialdirection in the case of the VB method or by adjusting the temperatureof each of heaters 24 a, 24 b in the case of the VGF method.Accordingly, molten InP source material 13 is sequentially solidifiedfrom the InP seed crystal 11 side, whereby an InP single-crystal isgrown. Molten InP source material 13 in the conical portion and straightbody portion of the crystal growth portion is entirely solidified inthis order, thereby forming the InP single crystal body. In the VBmethod, a moving speed (pulling-down speed) of crucible 21 is notparticularly limited, and can be, for example, more than or equal to 2.0mm/h and less than or equal to 5.0 mm/h.

It should be noted that in the method for manufacturing the InPsingle-crystal body in the present embodiment, as the diameter of thestraight body portion of the grown crystal body becomes larger, acontact area between the InP source material and the sealing member isgenerally increased. Hence, the oxygen concentration in the InP crystalis more likely to be higher. Moreover, the large diameter of the crystalbody leads to a large thermal stress during the crystal growth, with theresult that a dislocation density of the crystal body tends to be high.In the gradual temperature distribution condition effective to suppressthis, the temperature at the upper portion of the InP source materialbecomes low, with the result that stirring by convection currents ismore likely to take place. That is, when an InP crystal body is grown tohave a large diameter and a low dislocation density, an oxygenconcentration in the InP crystal body becomes higher. According to themethod for manufacturing the InP single-crystal body in the presentembodiment, oxygen can be suppressed from being incorporated into theInP source material because the contact area between the source materialand the sealing member is reduced by placing the closure plate and theconvection currents are reduced by an appropriate heater structure andheat environmental design.

<Second Embodiment: Indium Phosphide Single-Crystal Substrate>

An InP (indium phosphide) single-crystal substrate of the presentembodiment has an oxygen concentration of less than 1×10¹⁶ atoms cm⁻³,wherein a diameter of the InP single-crystal substrate is more than orequal to 100 mm and less than or equal to 150 mm or is more than 100 mmand less than or equal to 150 mm. Even though the diameter of the InPsingle-crystal substrate of the present embodiment is so large as to bemore than or equal to 100 mm and less than or equal to 150 mm or as tobe more than 100 mm and less than or equal to 150 mm, the oxygenconcentration is less than 1×10¹⁶ atoms·cm⁻³, which is very low.Accordingly, an oxide layer is suppressed from being formed in a surfaceof the InP single-crystal substrate and a composite state is suppressedfrom being formed in the InP single-crystal substrate, whereby asemiconductor device including the InP single-crystal substrate has highcharacteristics. The oxygen concentration of the InP single-crystalsubstrate is measured by SIMS (Secondary Ion Mass Spectrometry) as withthe InP single-crystal body of the first embodiment. Here, the oxygendetection limit concentration in SIMS is about 1×10¹⁶ atoms·cm ^(3.)Hence, the oxygen concentration of the InP single-crystal substrate ofthe present embodiment is less than the detection limit in SIMS, and aprecise oxygen concentration thereof is measured by CPAA (ChargedParticle Activation Analysis) or the like. In order to improve thecharacteristics of the semiconductor device by reducing the oxygenconcentration, the precise oxygen concentration of the InPsingle-crystal substrate of the present embodiment as obtained by theactivation analysis such as CPAA is preferably less than or equal to9.5×10¹⁵ atoms·cm⁻³, and is more preferably less than or equal to5.5×10¹⁵ atoms·cm⁻³. Moreover, a lower oxygen concentration is morepreferable. The lower limit of the oxygen concentration is notparticularly limited, but is more than or equal to 5×10¹⁴ atoms·cm ⁻³ inview of a current manufacturing technology level.

The diameter of the InP single-crystal substrate of the presentembodiment is more than or equal to 100 mm and less than or equal to 150mm. Even though the diameter of the InP single-crystal substrate is solarge as to be more than or equal to 100 mm and less than or equal to150 mm, the oxygen concentration of the InP single-crystal substrate isvery low. Accordingly, an oxide layer is suppressed from being formed ina surface of the InP single-crystal substrate and a composite state issuppressed from being formed in the InP single-crystal substrate,whereby a semiconductor device including the InP single-crystalsubstrate has high characteristics. The diameter of the InPsingle-crystal substrate is more than or equal to 100 mm, is preferablymore than 100 mm, and is more preferably more than or equal to 125 mm inorder to attain the low oxygen concentration even in the large-sized InPsingle-crystal substrate.

Although not particularly limited, a method for manufacturing the InPsingle-crystal substrate in the present embodiment preferably includes aprocessing step and a polishing step using the InP single-crystal bodyof the first embodiment in order to efficiently form an InPsingle-crystal substrate having an low oxygen concentration. In theprocessing step, the outer circumference of the InP single-crystal bodyis ground and the InP single-crystal body having been ground is slicedin an appropriately specified direction, thereby obtaining an InPsingle-crystal substrate having a main surface in the appropriatelyspecified plane orientation. Next, in the polishing step, the mainsurface of the InP single-crystal substrate is subjected to mechanicalpolishing and/or chemical mechanical polishing (CMP), thereby obtainingan InP single-crystal substrate having a main surface polished to be amirror surface.

EXAMPLES Example 1

1. Production of InP Single-Crystal Body

An InP single-crystal body is grown by the VB method. As shown in FIG.1, two heaters 24 a, 24 b are used and one inter-heater gap 24 abo isprovided. Closure plate 25 composed of PBN is placed between an InPpolycrystal body having a purity of 99.9 mass % and serving as InPsource material 13 and B₂O₃ serving as sealing member 23. The closureratio (percentage of the area of the closure plate with respect to thecross sectional area of the straight body portion of crucible 21perpendicular to the axial direction) of closure plate 25 is set to 97%.The InP single-crystal body is grown by adjusting a temperaturedistribution in the crucible to attain a temperature of 1065° C. at asurface of the InP source material and attain a temperature gradient of2° C./cm at a crystal growth interface in a crystal growth direction.

2. Production of InP Single-Crystal Substrate

The outer circumference of the obtained InP single-crystal body wasground and the obtained InP single-crystal body was sliced along a planeperpendicular to the crystal growth direction. Then, the main surfacethereof was subjected to mechanical polishing and chemical mechanicalpolishing (CMP), thereby producing InP single-crystal substrates eachhaving a diameter of 100 mm and a thickness of 525 μm. The oxygenconcentration of each of the obtained InP single-crystal substrates ismeasured by CPAA (Charged Particle Activation Analysis), the thicknessof an oxide film formed in the main surface is measured by a spectralellipsometer (PCA ellipsometer SE-101 provided by Photonic Lattice), anda dislocation density thereof is measured in an optical microscope image(BH2-UMA provided by Olympus). Further, emission intensities of oxygendefect centers in the InP crystal substrate are measured by a cathodeluminescence measuring device (MonoCL4 provided by Gatan). Results arecollectively shown in Table 1.

Here, in the CPAA for the oxygen concentration, ¹⁸F is used which isgenerated by a nuclear reaction between ³He and oxygen, ¹⁶O, in the InPcrystal body and which undergoes β^(|) decay with a half-life of 109.73minutes. The InP crystal body having been irradiated with ³He is meltedwith an acid, and ¹⁸F generated by way of a KBF₄ (potassiumtetrafluoroborate) precipitation method is chemically separated. Gammarays of 511 keV, which are generated by positron annihilation upon theβ⁺ decay of¹⁸F, are measured using a NaI detector to determine thenumber of counts for a specified time after the end of the irradiationby the least squares method. The number of counts after the specifiedtime as determined using a standard sample, SiO₂, in the same manner isused for correction, thereby converting it to the oxygen concentration.

Moreover, a peak emission intensity (emission wavelength: around 1078nm) of the oxygen defect centers in the InP crystal substrate ismeasured at a room temperature (25° C.) with the cathode luminescence(acceleration voltage: 5 kV; electron current: 0.4 nA; beam diameter: 10nm), whereby an amount of the oxygen defect centers in the InP crystalsubstrate can be evaluated. When the amount of the oxygen defect centersis smaller than 500 counts/sec, the emission intensity of the oxygendefect centers in the InP crystal substrate is regarded as “Small”. Whenthe amount of the oxygen defect centers is larger than 5000 counts/sec,the emission intensity of the oxygen defect centers in the InP crystalsubstrate is regarded as “Large”. When the amount of the oxygen defectcenters is more than or equal to 500 counts/sec and less than or equalto 5000 counts/sec, the emission intensity of the oxygen defect centersin the InP crystal substrate is regarded as “Appropriate”. When theemission intensity of the oxygen defect centers in the InP crystalsubstrate is not “Large” and “Small” but is “Appropriate”, growth fromthe oxygen defect centers is facilitated during the crystal growth andtherefore abnormal defects are less likely to be generated. “Small” isthe second most preferable to “Appropriate”. In the case of “Large”,electron mobility in the InP single-crystal body becomes low, thusresulting in decreased characteristics of a device including the InPsingle-crystal substrate.

Example 2

An InP single-crystal body and an InP single-crystal substrate areproduced in the same manner as in Example 1 except that the closureratio of the closure plate is set to 90%, and the oxygen concentrationthereof, the thickness of the oxide film thereof, the dislocationdensity thereof, and the emission intensity of the oxygen defect centerstherein are measured. Results are collectively shown in Table 1.

Comparative Example 1

Production of an InP single-crystal body and an InP single-crystalsubstrate is attempted in the same manner as in Example 1 except thatthe closure ratio of the closure plate is set to 100%; however, theclosure plate is caught in the crucible and the crucible is broken dueto volume expansion resulting from crystal solidification, with -theresult that no excellent InP single-crystal body is obtained. Resultsare collectively shown in Table 1.

Comparative Example 2

An InP single-crystal body and an InP single-crystal substrate areproduced in the same manner as in Example 1 except that the closureratio of the closure plate is set to 80%, and the oxygen concentrationthereof, the thickness of the oxide film thereof, the dislocationdensity thereof, and the emission intensity of the oxygen defect centerstherein are measured. Results are collectively shown in Table 1.

Example 3

An InP single-crystal body and an InP single-crystal substrate areproduced in the same manner as in Example 1 except that the closureratio of the closure plate is set to 99%, and the oxygen concentrationthereof, the thickness of the oxide film thereof, the dislocationdensity thereof, and the emission intensity of the oxygen defect centerstherein are measured. Results are collectively shown in Table 1.

Comparative Example 3

An InP single-crystal body and an InP single-crystal substrate areproduced in the same manner as in Example 1 except that two inter-heatergaps are provided, the closure ratio of the closure plate is set to 20%,and the temperature of the surface of the InP source material is set to1070° C., and the oxygen concentration thereof, the thickness of theoxide film thereof, the dislocation density thereof, and the emissionintensity of the oxygen defect centers therein are measured. Results arecollectively shown in Table 1.

Comparative Example 4

An InP single-crystal body and an InP single-crystal substrate areproduced in the same manner as in Example 1 except that fourinter-heater gaps are provided and the closure ratio of the closureplate is set to 20%, and the oxygen concentration thereof, the thicknessof the oxide film thereof, the dislocation density thereof, and theemission intensity of the oxygen defect centers therein are measured.Results are collectively shown in Table 1.

Comparative Example 5

An InP single-crystal body and an InP single-crystal substrate areproduced in the same manner as in Example 1 except that fourinter-heater gaps are provided and no closure plate is placed, and theoxygen concentration thereof, the thickness of the oxide film thereof,the dislocation density thereof, and the emission intensity of theoxygen defect centers therein are measured. Results are collectivelyshown in Table 1.

Example 4

An InP single-crystal body and an InP single-crystal substrate areproduced in the same manner as in Example 1 except that the diameter ofthe InP single-crystal substrate is 125 mm, and the oxygen concentrationthereof, the thickness of the oxide film thereof, the dislocationdensity thereof, and the emission intensity of the oxygen defect centerstherein are measured. Results are collectively shown in Table 1.

Example 5

An InP single-crystal body and an InP single-crystal substrate areproduced in the same manner as in Example 2 except that the diameter ofthe InP single-crystal substrate is 125 mm, and the oxygen concentrationthereof, the thickness of the oxide film thereof, the dislocationdensity thereof, and the emission intensity of the oxygen defect centerstherein are measured. Results are collectively shown in Table 1.

Example 6

An InP single-crystal body and an InP single-crystal substrate areproduced in the same manner as in Example 1 except that the diameter ofthe InP single-crystal substrate is 150 mm, and the oxygen concentrationthereof, the thickness of the oxide film thereof, the dislocationdensity thereof, and the emission intensity of the oxygen defect centerstherein are measured. Results are collectively shown in Table 1.

Example 7

An InP single-crystal body and an InP single-crystal substrate areproduced in the same manner as in Example 2 except that the diameter ofthe InP single-crystal substrate is 150 mm, and the oxygen concentrationthereof, the thickness of the oxide film thereof, the dislocationdensity thereof, and the emission intensity of the oxygen defect centerstherein are measured. Results are collectively shown in Table 1.

TABLE 1 Compar- Compar- Compar- Compar- Compar- ative ative ative ativeative Exam- Exam- Exam- Exam- Exam- Exam- Exam- Exam- Exam- Exam- Exam-Exam- ple 1 ple 2 ple 1 ple 2 ple 3 ple 3 ple 4 ple 5 ple 4 ple 5 ple 6ple 7 Closure Ratio 97 90 100 80 99 20 20 0 97 90 97 90 of Closure Plate(%) Number of 1 1 1 1 1 2 4 4 1 1 1 1 Inter-Heater Gaps Diameter of 100100 100 100 100 100 100 100 125 125 150 150 InP Single- CrystalSubstrate (mm) Oxygen 5.50 × 9.50 × — 2.80 × 1.00 × 3.25 × 5.55 × 8.87 ×7.50 × 8.50 × 9.10 × 9.80 × Concentration 10¹⁵ 10¹⁵ 10¹⁶ 10¹⁵ 10¹⁶ 10¹⁶10¹⁶ 10¹⁵ 10¹⁵ 10¹⁵ 10¹⁵ of InP Single- Crystal Substrate (atoms · cm⁻³)Thickness of 0.34 0.95 — 1.20 0.15 1.51 1.83 2.11 0.80 0.96 0.90 0.98Oxide Film of InP Single- Crystal Substrate (nm) Dislocation 2500 2500 —2500 2500 4000 2500 2500 3000 3000 3500 3500 Density (cm⁻²) EmissionAppro- Appro- — Large Small Large Large Large Appro- Appro- Appro-Appro- Intensity of priate priate priate priate priate priate OxygenDefect Centers

With reference to Table 1, as shown in Example 1 to Example 7, theoxygen concentration could be reduced to less than 1×10¹⁶atoms·cm ⁻³ ineach of the InP single-crystal bodies and the InP single-crystalsubstrates produced with one inter-heater gap being provided and theclosure plate being placed at a closure ratio of 90% to 99%. Moreover,in each of these InP single-crystal substrates, the thickness of theoxide film of the main surface thereof could be as thin as 0.15 nm to0.98 nm, the dislocation density could be also as low as 2500 cm⁻² to3500 cm ², and the emission intensity of the oxygen defect centers inthe substrate could be appropriate (suitable), not large or small. Sincethe oxygen concentration is so low as to be less than 1×10¹⁶ atoms·cm³,the thickness of the oxide film of the main surface is as thin as 0.15nm to 0.98 nm, and the emission intensity of the oxygen defect centersin the crystal is not too large or too small but is appropriate(suitable) in each of these InP single-crystal substrates, a compositestate can be suppressed from being formed in the substrate, a responsespeed as a semiconductor device can be suppressed from being reduced,and resistance of a semiconductor device including an epitaxial layergrown on the substrate can be reduced. It should be noted that in viewof a comparison among Example 1, Example 4, and Example 6, it was foundthat as the diameter of the InP single-crystal substrate becomes larger,the thickness of the oxide film and the dislocation density becomelarger.

In Comparative Example 1, one inter-heater gap was provided but theclosure plate was placed at a closure ratio of 100%, with the resultthat the closure plate was caught in the crucible and the crucible wasbroken due to the volume expansion resulting from the crystalsolidification as described above. Accordingly, no excellent InPsingle-crystal body was obtained. Moreover, in Comparative Example 2,the surface temperature of the InP source material was high and it wasexpected to suppress melt convection currents; however, the oxygenconcentration of each of the InP single-crystal body and the InPsingle-crystal substrate could not be less than 1×10¹⁶ atoms·cm³ and thedislocation density thereof became high. Moreover, in each ofComparative Example 3 and Comparative Example 4, two or fourinter-heater gaps were provided and the closure plate being placed at aclosure ratio of 20%; however, the oxygen concentration of each of theInP single-crystal body and the InP single-crystal substrate could notbe less than 1×10¹⁶ atoms·cm⁻³. Moreover, in Comparative Example 5, thetypical conditions in which four inter-heater gaps were provided and noclosure plate was placed were employed, with the result that the oxygenconcentration of each of the InP single-crystal body and the InPsingle-crystal substrate became high.

The embodiments and examples disclosed herein are illustrative andnon-restrictive in any respect. The scope of the present invention isdefined by the terms of the claims, rather than the embodiments andexamples described above, and is intended to include any modificationswithin the scope and meaning equivalent to the terms of the claims.

REFERENCE SIGNS LIST

11: InP seed crystal; 13: InP source material; 20, 30: manufacturingapparatus; 21, 31: crucible; 21 c, 31 c: oxide film; 22, 32: crucibleholder; 23, 33: sealing member; 24 a, 24 b, 34 a, 34 b, 34 c, 34 d:heater; 24 abo, 34 abo, 34 bco, 34 cdo: inter-heater gap; 25: closureplate; 25o: opening; 26, 36: chamber.

1. An indium phosphide single-crystal body having an oxygenconcentration of less than 1×10¹⁶ atoms·cm⁻³, the indium phosphidesingle-crystal body comprising a straight body portion having acylindrical shape, wherein a diameter of the straight body portion ismore than or equal to 100 mm and less than or equal to 150 mm.
 2. Theindium phosphide single-crystal body according to claim 1, wherein thediameter of the straight body portion is 100 mm.
 3. An indium phosphidesingle-crystal substrate having an oxygen concentration of less than1×10¹⁶ atoms·cm⁻³, wherein a diameter of the indium phosphidesingle-crystal substrate is more than or equal to 100 mm and less thanor equal to 150 mm.
 4. (canceled).
 5. The phosphide single-crystalsubstrate according to claim 3, wherein the diameter of the indiumphosphide single-crystal substrate is 100 mm.
 6. The indium phosphidesingle-crystal substrate according to claim 3, wherein a dislocationdensity of the indium phosphide single-crystal substrate is less than orequal to 3500 cm⁻².
 7. The phosphide single-crystal substrate accordingto claim 6, wherein the diameter of the indium phosphide single-crystalsubstrate is 100 mm.